1. Field of the Invention
The present invention relates to a gripper for parts having a different shape in a surface mount device, and in particular to an improved gripper for parts having a different shape which can easily pick up the parts, transfer the parts to a printed circuit board, and mount the parts on the printed circuit board when a surface mount device mounts the parts on the printed circuit board.
2. Description of the Background Art
A surface mount device is used to rapidly precisely mount a plurality of parts on a printed circuit board. A structure of the surface mount device for rapidly precisely mounting parts on the printed circuit board will now be explained with reference to the accompanying drawings. FIG. 1 is a plan view illustrating the surface mount device. As shown therein, the surface mount device 10 includes an X-Y gantry 11, a printed circuit board conveyor 12, a module head 13 and a nozzle exchanger 14.
The X-Y gantry 11 transfers the module head 13 in an X-Y axis direction. The module head 13 transferred by the X-Y gantry 11 in the X-Y axis direction transfers parts to a printed circuit board 1. The printed circuit board 1 is transferred to a mounting operation position A by the printed circuit board conveyor 12. When the printed circuit board 1 is transferred to the mounting operation position A by the printed circuit board conveyor 12, the module head 13 sucks the parts, transfers the parts to the printed circuit board 1, and mounts the parts on the printed circuit board 1.
The module head 13 sucking the parts and transferring the sucked parts to the printed circuit board 1 includes a plurality of nozzle apparatuses 20. A structure of the nozzle apparatus 20 will now be explained with reference to FIG. 2. Referring to FIG. 2, the nozzle apparatus 20 includes a socket unit 21 and a holder unit 22. The socket unit 21 includes a hollow shaft 21a, an assembly block 21b, a connection block 21c, a socket shaft 21d and an elastic member 21e. The holder unit 22 includes a holder 22a and a holder shaft 22b. 
The hollow shaft 21a of the socket unit 21 has a hollow, and the connection block 21c is installed by the assembly block 21b formed on the bottom surface of the hollow shaft 21a. The holder 22a of the holder unit 22 is moved to the inner portion of the connection block 21c moved by the assembly block 21b. The socket shaft 21d and the elastic member 21e are disposed on the bottom surface of the connection block 21c in order to firmly and removably support the holder 22a moved to the inner portion of the connection block 21c. 
The socket shaft 21d of the connection block 21c is supported at both side portions of the connection block 21c by the elastic member 21e. The socket shaft 21d supported by the elastic member 21e and moved to a slanted surface of the connection block 21c supports both side portions of the holder 22a of the holder unit 22 in movement. The holder shaft 22b is formed on the bottom surface of the holder 22a having its side portions supported by the socket shaft 21d. 
When the holder 22a is moved to the inner portion of the connection block 21c, a nozzle (not shown) is mounted on the holder shaft 22b. In this state, a component is adsorbed by the nozzle, transferred to the printed circuit board 1, and mounted thereon. To replace the holder unit 22, the socket unit 21 is moved to the nozzle exchanger (14 in FIG. 1), and rapidly moved in a vertical direction to pick up the holder unit 22 disposed at the nozzle exchanger 14, thereby mounting and replacing the holder unit 22. The nozzle (not shown) is mounted at the inner portion of the holder shaft 22b of the replaced holder unit 22.
The nozzle in the conventional art is formed to pick up surface mounting parts having a constant shape and size and to mount the parts on the printed circuit board, and thus it is difficult to grip parts having a different shape and size.
Accordingly, it is a primary object of the present invention to provide a gripper for parts having a different shape which can pick up parts having a variable shape and size in a surface mount device, and mount the parts on a printed circuit board.
Another object of the present invention is to easily pick up parts having a different shape by providing a gripper for the parts, and easily mount the parts on a printed circuit board.
In order to achieve the above-described objects of the invention, there is provided a gripper for parts having a different shape comprising: a holder having one end mounted and moved in a socket unit, and having a penetration groove forming a passage of air flown through the socket unit; a piston mounted in the penetration groove, and lifted or lowered due to a pressure of the air flown through the penetration groove; a movement unit being installed at both side ends of the other end of the holder, and having a slanted surface to be horizontally moved in a direction of increasing or decreasing an interval by the piston lifted or lowered due to the air flown through the penetration groove; and a plurality of grip tips fixed to the movement unit, and engaged with the horizontal movement of the movement unit, for picking up or putting the parts.